A third former teacher at Shattuck-St. Mary's School in Faribault has been accused of sexual misconduct with a student -- this time in 1980 -- and authorities are investigating a fourth case involving an employee at the college-prep boarding and day school.

Criminal charges against Joseph C. Machlitt, 63, of St. Paul, say the former dorm parent and art teacher had sex with a 14-year-old male student. Machlitt was arrested Tuesday.

School officials said they were "appalled" by the new charges, which were filed just seven weeks after Lynn Seibel, a former drama teacher at the school, was charged with sexually abusing six boys between 1999 and 2003. Authorities also say that Len Jones, a teacher who committed suicide in 2008, had been accused of having a three-year sexual relationship with a teenage female exchange student.

Machlitt was charged Wednesday in Rice County District Court with one count of third-degree criminal sexual conduct and one count of attempted fourth-degree criminal sexual conduct, both felonies.

He could face more charges in the future. Faribault police Capt. Neal Pederson said on Wednesday that authorities have identified another former student allegedly abused by Machlitt.

Pederson also said authorities are investigating a fourth employee of Shattuck-St. Mary's who allegedly abused a student between 1980 and 1992.

All four cases are apparently unrelated, Pederson said.

Faribault police spokesman Don Gudmundson, a former interim chief of the department, said in a written statement Wednesday that "police believe [that] at the time of the incidents, Shattuck-St. Mary's administrators and staff were not aware of the sexual abuse" by Machlitt. Gudmundson had been critical of school officials for not sharing their knowledge of the allegations against Jones and Seibel.

Charges prompted victim

According to the criminal complaint against Machlitt, the accuser -- a 46-year-old Minnesota man identified as "JJ" -- came forward on Oct. 9 after seeing news reports and social network chatter about the charges against Seibel. The man told Faribault police that he started summer school at Shattuck-St. Mary's in the summer of 1980. He was swimming in the pool on June 25 and hit his head.

Machlitt took him to the hospital and agreed to take care of him that evening, as it was believed the boy had a concussion. Machlitt brought the boy back to his school apartment, where the boy fell asleep on the sofa. When he awoke, Machlitt was massaging his legs, according to the criminal charges. That progressed to Machlitt's touching the boy's genitals and performing oral sex on him, the charges say.

"JJ" told police there were two other incidents inside Machlitt's apartment. During one, Machlitt allegedly rubbed the boy's back and touched him while they talked. During the other, Machlitt tried touching the boy's genitals but the boy pushed him away, the complaint said.

"The defendant asked why it was all right to touch him the first time, but not this time," the complaint said. "JJ responded that he was not comfortable with it."

The complaint said the accuser didn't tell anyone about the abuse until he was 29, when he told several therapists.

Machlitt was interviewed on Oct. 18 by agents from the state Bureau of Criminal Apprehension and denied having any sexual contact with the former student, according to the complaint. But five days later, he returned and admitted that he "had a sexual relationship with a student," the complaint said.

In early October, Gudmundson lambasted Shattuck-St. Mary's, saying the Jones incident was part of "a pattern of past history with the school" of not notifying police about possible criminal allegations, including alleged sexual abuse by Seibel.

Behavior 'offensive, wrong'

On Wednesday, Jon Austin, a public relations consultant, sent a statement from the school saying, "Like anyone, we're appalled by the alleged actions, which the school learned of for the first time today, involving a former employee who left the school in 1980. The behavior described in the complaint is offensive, wrong and violates our code of conduct."

The storied 154-year-old boarding school is known as a hub for elite athletes and future leaders, including prominent alumni Hubert "Skip" H. Humphrey and hockey players Sidney Crosby and Zach Parise. The school has 439 students. Annual boarding tuition for U.S. students is $40,450.

Machlitt told investigators that he left Shattuck-St. Mary's in 1980 to take a job at a school in New Hampshire. He worked at St. Paul's School in Concord, N.H., for four years and lived in New Hampshire for five. He and his wife now live in St. Paul, and he worked during the 2010-2011 school year as a math and English tutor for A+ Tutoring Service, based in Woodbury.

Owner Bonnie Vander Vegte said her company does criminal background and sex offender checks for all of its employees.

"There was nothing" on Machlitt, she said.

"We do not let anyone work for us until those background checks are back." She added: "Our tutors never work alone with a child."

If Machlitt is convicted, he'll face a presumptive sentence of 24 months on the third-degree charge and a 21-month stayed sentence on the attempted fourth-degree charge, under Minnesota sentencing guidelines in effect in 1980.